Watch having tuning fork time standard

ABSTRACT

A watch having a tuning fork vibrating at an audio frequency as a time standard is provided with means for converting the vibratory movement of the tuning fork into the rotary movement of a gear train and a driving circuit for sustaining the vibratory movement of the tuning fork. The driving circuit includes a battery, a two-terminal coil cooperating with a magnetic circuit on said tuning fork, a PNP transistor and an NPN transistor, the two-terminal coil being connected between the collector electrodes of said transistors.

United States Patent 1 1 3,780,520 Tsuruishi Dec. 25, 1973 [54] WATCH HAVING TUNING FORK TIME 3,596,461 8/1971 Reich 58/28 A STANDARD Yuki Tsuruishi, Suwa, Japan Kabushiki Kaisha Suwa Seikasha, Tokyo, Japan Filed: Feb. 2, 1972 Appl. No.: 222,956

lnventor:

Assignee:

Foreign Application Priority Data Feb. 12, 1971 Japan...... 46/5577 US. Cl. 58/23 TF, 3l8/l27 Int. Cl...' G04c 3/00 Field of Search 58/23 A, 23 TF, 23 V,

58/28 AB, 28 D; 318/127-129, 133

References Cited UNITED STATES PATENTS Baumgartner 58/23 TF Primary Examiner-Richard B. Wilkinson Assistant Examiner-Edith Simmons Jackmon Attorney-Alex Friedman et al.

[57] ABSTRACT A watch having a tuning forkvibrating at an audio frequency as a time standard is provided with means for converting the vibratory movement of the tuning fork into the rotary movement of a gear train and a driving circuit for sustaining the vibratory movement of the tuning fork. The driving circuit includes a battery, a two-terminal coil cooperating with a magnetic circuit on said tuning fork, a PNP transistor and an NPN transistor, the two-terminal coil being connected between the collector electrodes of said transistors.

3 Claims, 3 Drawing Figures WATCH HAVING TUNING FORK TIME STANDARD BACKGROUND OF THE INVENTION This invention relates to watches incorporating tuning forks as the time standard. Such tuning fork time standards have the advantage of operating at low power losses. In conventional watches incorporating tuning forks, the tuning fork-is vibrated by a driving circuit which forms a feedback amplifier with a detecting coil and a driving coil. Since two separate coils are required, assembly is difficult, the arrangement of the tuning fork is restricted, and driving efficiency is lowered since the number of turns of the driving coil must be limited to provide space for the detecting coil.

SUMMARY OF THE INVENTION Generally speaking, in accordance with the invention, a watch having a tuning fork time standard vibratable at audio frequencies is provided. Means are provided for converting the vibratory movement of said tuning fork into a rotary movement of a gear train for time indication. The tuning fork is provided with a magnetic circuit, and a two-terminal drive coil is positioned in the field of said magnetic circuit for cooperation therewith to sustain the oscillation of said tuning fork when suitable driving pulses are applied to said driving coil. A driving circuit includes a battery, an NPN transistor, a PNPtransistor, and said two-terminal drive coil, said drive coil being connected between the respective collectors of said transistors.

Accordingly, it is an object of this invention to provide a self-starting circuit for driving a tuning fork which is operated at low power levels.

It is a further object of this invention to provide a watch incorporating a simplified tuning fork time standard structure, and in particular, a structure incorporating a single driving coil of maximum number of turns to prolong battery life.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWING For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawing, in which:

FIG. 1 is a top plan view of the structure of a watch in accordance with the invention, incorporating a tuning fork time standard;

FIG. 2 is a circuit diagram of the driving circuit according to the invention; and

FIG. 3 is a graphical representation of the relation between consumption energy and vibration amplitude for the arrangement in accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, the watch incorporating a tuning fork time standard depicted includes a tuning fork 1 adapted to vibrate at an audio frequency and mounted on the plate of the watch by means of screws 14. A U-shaped magnetic circuit is formed on the end of each tine of tuning fork l by a pair of spaced magnetic plates 6 mounted at one end to the end of each tine. A pair of semicircular permanent magnets 7 are mounted in facing relation on the inner surfaces of magnetic plates 6 to complete said magnetic circuit. The magnetic flux in each circuit runs through magnetic plates 6, the end of the tine of tuning fork 1, through the pair of permanent magnets and the space therebetween. A flat round coil 5 is inserted in the space between said pairs of permanent magnets defined by the two U-shaped magnetic circuits. Coil 5 is a driving coil mounted on a coil frame 4 which serves both to mount the terminals of coil 5 and for connecting a battery 2 with a baseplate 8 carrying the driving circuit. Thus, one pole of battery 2 is connected to the plate of the watch, while the negative pole of the battery is connected by means of spring 3 through a conductive layer deposited on coil frame 4 to a conductivev layer 13 on circuit baseplate 8. Said circuit baseplate is coupled with the plate of the watch by means of a screw 12, and is connected to the positive pole of the battery through said watch plate.

Tuning fork 1 is provided with a feed spring 10 which rotates a ratchet wheel 9. A click 11 engages ratchet wheel 9 to prevent the reverse rotation thereof.

Referring to FIG. 2, the driving circuit of the arrangement of FIG. 1 is depicted, the electronic components of said circuit except for the drive coil and the battery being mounted on circuit baseplate 8. In said circuit, a PNP transistor 1 I5 is connected with its emittercollector path in series with drive coil 19 (which corresponds to coil 5 in FIG. I) and the emitter-collector path of NPN transistor 17. Said series connection is connected across battery 22 (which corresponds to battery 2 of FIG. 1). A trigger condenser 17 is connected between the collector of transistor 15 and the base of transistor 16. Base bias resistor 18 is connected between the base of transistor 16 and the collector of transistor 15, while base bias resistor 21 is connected between the base of transistor 15 and the collector of transistor 16. A condenser 20 is connected between the base and collector of transistor 15 to prevent oscillation of the harmonic wave.

The circuit of FIG. 2 may be classified as a blocking oscillator and is of the self-running type. Thus, said circuit oscillates even though tuning fork 1 is not vibrating. If the operating frequency of the circuit of FIG. 2 is selected so as to be almost that of tuning fork 1, said tuning fork can easily self-start. Coil 19 serves both as a detecting and driving coil, so that a separate detecting coil is not required, and so that a maximum number of turns of the driving coil may be wound in the space between the permanent magnets 7. This arrangement permits the driving of the tuning fork at relatively low power levels.

This point is demonstrated by FIG. 3, wherein a graphical representation between power and maximum amplitude of vibration of the tuning fork tines is depicted. In said figure, the axis of abscissa represents maximum vibration amplitude A while the axis of ordinates represents energy AP and AE. Curves 23 and 24 show the relationship between AE and A,,. When the oscillating frequency f is increased, the consumption energy sharply increases with relatively small increases in amplitude. Curves 25 and 26 show the relationship between energy AP supplied from the driving circuit to the tuning fork and the maximum amplitude A The tuning fork is stabilized at the point where AB AP, for example at points P, Q, R and S.

K refers to the product Bnl with regard to curves 25 and 26, wherein B represents the flux density of the magnetic circuit, n represents the turns of the driving coil and 1 represents the mean effective length of the winding of the driving coil. When the value Bnl is increased, a greater increase in amplitude is required to change AP. Thus, if the number of turns of the driving coil n is increased, the tuning fork can be driven with relatively low electric power drain, and the oscillating frequency f of the turning fork can be increased as required.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended, that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

What is claimed is:

l. A watch comprising tuning fork means for vibrating at an audio frequency to define a time standard; a gear train; means for converting the vibratory movement of said tuning fork means into rotary movement of said gear train; a battery; a magnetic circuit mounted on said tuning fork means for vibration therewith; a two-terminal drive coil positioned for cooperation with said magnetic circuit for driving said magnetic circuit in response to driving current supplied to said drive coil; driving circuit means powered by said battery for producing an oscillating driving current in said drive coil, said driving circuit means including a PNP transistor and a NPN transistor, said two terminal drive coil being connected between the respective collectors of said transistors, coil frame means releasably mounted in said watch and carrying said drive coil and electrical conductor means for electrically connecting said battery and drive coil to said driving circuit means; circuit base plate means separate from said coil frame means and releasably mounted in said watch, said circuit plate means carrying said driving circuit means; and means releasably electrically connecting said battery, said electrical conductor means on said coil frame means and said driving circuit means on said circuit plate means.

2. A watch as recited in claim 1, including a first condensor connected between the collector and base of one of said transistors for preventing oscillation of the harmonic wave; a first base biased resistor connected between the base of said PNP transistor and the collector of said NPN transistor; a second base biased resistor connected between the base of said NPN transistor and the collector of said PNP transistor; and a second condensor connected between the collector electrode of one of said transistors and the base electrode of the other of said transistors, the emitter electrode of said PNP transistor being connected to the positive of said battery, the emitter of. said NPN transistor being connected to the negative of said battery.

3. A watch as recited in claim 1, wherein said battery and circuit plate means are mounted on opposed sides of said tuning fork means within said watch with said coil frame means mounted intermediate said battery and circuit plate means. 

1. A watch comprising tuning fork means for vibrating at an audio frequency to define a time standard; a gear train; means for converting the vibratory movement of said tuning fork means into rotary movement of said gear train; a battery; a magnetic circuit mounted on said tuning fork means for vibration therewith; a two-terminal drive coil positioned for cooperation with said magnetic circuit for driving said magnetic circuit in response to driving current supplied to said drive coil; driving circuit means powered by said battery for producing an oscillating driving current in said drive coil, said driving circuit means including a PNP transistor and a NPN transistor, said two terminal drive coil being connected between the respective collectors of said transistors, coil frame means releasably mounted in said watch and carrying said drive coil and electrical conductor means for electrically connecting said battery and drive coil to said driving circuit means; circuit base plate means separate from said coil frame means and releasably mounted in said watch, said circuit plate means carrying said driving circuit means; and means releasably electrically connecting said battery, said electrical conductor means on said coil frame means and said driving circuit means on said circuit plate means.
 2. A watch as recited in claim 1, including a first condensor connected between the collector and base of one of said transistors for preventing oscillation of the harmonic wave; a first base biased resistor connected between the base of said PNP transistor and the collector of said NPN transistor; a second base biased resistor connected between the base of said NPN transistor and the collector of said PNP transistor; and a second condensor connected between the collector electrode of one of said transistors and the base electrode of the other of said transistors, the emitter electrode of said PNP transistor being connected to the positive of said battery, the emitter of said NPN transistor being connected to the negative of said battery.
 3. A watch as recited in claim 1, wherein said battery and circuit plate means are mounted on opposed sides of said tuning fork means within said watch with said coil frame means mounted intermediate said battery and circuit plate means. 